Lifestyle interventions have shown limited effectiveness in the prevention of gestational diabetes mellitus. The combination of lifestyle interventions with omega-3 polyunsaturated fatty acid supplementation could have a synergetic effect on maternal and offspring outcomes.

We evaluated the effects of docosahexaenoic acid supplementation among obese and overweight pregnant women (independently or combined with a dietary counseling intervention) on metabolic control in mothers and their offspring.

This study was a randomized controlled trial with a 2×2 factorial design. The following inclusion criteria were used: <15 weeks of gestation; body mass index ≥25 kg/m² at the first prenatal visit; singleton pregnancy; and 18 years of age or older. The recruited women (n=1002) were randomly allocated to 1 of the 4 parallel groups: Group 1: dietary counseling plus 800 mg/day of docosahexaenoic acid (n=250); Group 2: routine counseling plus 800 mg/day docosahexaenoic acid (n=252); Group 3: dietary counseling plus 200 mg/day docosahexaenoic acid (n=249); and Group 4: routine counseling plus 200 mg/day docosahexaenoic acid (n=251), considered as the reference group. The dietary intervention comprised 3 sessions, and it was focused on reducing the consumption of foods that most contributed to daily sugar intake. Primary outcomes were gestational diabetes mellitus defined according to the national guidelines; macrosomia (birthweight >4000 g); and neonatal insulin resistance (cord blood Homeostasis Model Assessment for Insulin Resistance ≥2.60), which was assessed in a subsample of 226 newborns. The analysis was by intention to treat and by efficacy. The trial was registered on ClinicalTrials.gov (NCT02574767).

The overall incidence of gestational diabetes mellitus was 20.2% (Group 1, 21.0%; Group 2, 20.1%; Group 3, 18.9%; and Group 4, 20.9%). Mean birthweight was 3403.0 g (standard deviation, 575.3), and the incidence of macrosomia was 11.9% (Group 1, 13.2%; Group 2, 10.8%; Group 3, 11.5%; and Group 4, 12.1%). Median cord blood Homeostasis Model Assessment for Insulin Resistance was 0.9 (interquartile range, 0.6–1.7), and 10.2% showed cord blood insulin resistance (Group 1, 12.0%; Group 2, 12.0%; Group 3, 9.7%; and Group 4, 5.1%). No significant differences were found among groups regarding primary outcomes (P<.05). Glucose concentrations in the cord blood samples were lower in those adherents to the docosahexaenoic acid supplementation (P<.05).

For women who were overweight or obese at the beginning of pregnancy, this combined intervention did not reduce the risk of gestational diabetes in mothers or macrosomia and insulin resistance in neonates.